1. Field of the Invention
This invention relates to a method and apparatus for necking a metal container, such as a beverage container, to establish a unique configuration within the necked-in area and to the resultant container construction.
2. Description of the Prior Art
It has been known with respect to beverage cans to provide an integrally formed bottom, and a generally cylindrical body portion which terminates in an opening to which a separately formed can end may be secured. It has been known in respect of such containers to provide a reduced diameter portion adjacent the end to be opened to permit access to the contents of the container open end. See generally U.S. Pat. Nos. 4,457,158 and 4,781,047. It has also been known to form such necked-in container portions by spinning and to provide flanges at the free ends thereof. See generally U.S. Pat. Nos. 4,058,998, 4,435,969, 4,927,043 and 4,512,172.
It has also been known in connection with such necked-in portions, created by a conventional process, to provide residual annular ribs. See generally U.S. Pat. Nos. 4,403,493 and 4,578,007. Such ribs in the necked-in portion may project radially outwardly beyond the diameter of the remainder of the container body. See U.S. Pat. Nos. 4,870,847 and 4,927,043.
It has also been known to provide multiple necked-in containers which have a plurality of circumferential ribs. See U.S. Pat. Nos. 4,519,232, 4,693,018 and 4,732,027.
Various forms of equipment and dies for effecting necking of portions of cylindrical metal containers such as, for example, aluminum drawn and ironed containers have been disclosed in the patents referred to hereinbefore. See U.S. Pat. Nos. 4,310,110, 4,563,887 and 4,760,725.
U.S. Pat. No. 4,527,412 discloses an aerosol container which has a restricted neck established by multiple forming processes to create a welded container structure having a domed restricted opening.
U.S. Pat. No. 3,757,558 discloses apparatus for necking in tubular members wherein clearance is provided between the outer die and the inner die in order to reduce friction and compressive forces on the container walls and thereby resist scratches, scores and other defects in the result container product.
U.S. Pat. No. 4,774,839 discloses the necking of container walls in a plurality of stages in order to produce a smooth neck configuration which has a straight angularly disposed necked-in portion separating two curved portions.
Despite the foregoing known methods and apparatus there remains a very real and substantial need for an improved method and apparatus for creating necked-in containers such as beverage containers which have adequate strength, are substantially wrinkle free and devoid of annular rings have an aesthetically pleasing appearance.